Electrohydraulic actuator



March 23, 1965 H. (5. FARLEY ELECTROHYDRAULIC ACTUATOR 3 Sheets-Sheet 1Filed May 24, 1962 NB MPO INVENTOR.

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A 7' RIVAFYS" 5 Sheets-Sheet 3 Filed May 24, 1962 I AMPLIFIER DEVICENCTIO I SERVO A25 VALVE TAPE RECORDER XHYDRAULK: CYLINDER VOLT METERFIG.6.

INVENTOR HOWARD G. FARLEY BY TTORNEY S United States Patent 3,175,094 IELECTROHYDRAULIC ACTUATOR Howard G. Farley, Detroit, Mich., assignor toGuerin Engineering, Inc., Ferndale, Mich., a corporation of MichiganFiled May 24, 1962, Ser. No. 197,449 20 Claims. (Cl. 290-1) Thisinvention relates to power transmission and is particularly adaptable tothose of the type comprising two or more fluid pressure energytranslating devices, one of which may function as a pump and another asa fluid motor.

More particularly, this invention relates to electrically reproducingand recording the relative motion of a piston or the like and acylinder, which motion produces a variable voltage or amperage output.

This invention further relates to an electro-fluid actuator which emitsan electrical signal that is proportional to an increment of stroke. Thegenerated signal has a wide range and is of an amplitude that readingsor recordings can be taken directly from the cylinder lead.

One form of the electro-fluid actuator just mentioned consists of acylinder and piston device in which a transducer assembly is mounted onthe same axis and integral with the piston of said device. An elongatedstylus is mounted in the cylinder along the longitudinal axis thereofand is provided with a taper on one side thereof. By suitable means theconstantly varying cross sectional area of the stylus or the effectivedepth of the stylus is transmitted to the transducer so that aproportionate output signal is generated for each increment of stroke.

The output signal is properly amplified and delineated through and outof the cylinder by means of a cable around which an elastic tube orshroud is coiled for providing protection for the cable. The outputsignal thus generated is available to perform any task of control orreadout that may be required. As an example, the actuator can be used asa remote control device for operating levers, chutes, rolls, dampers,and other mechanical devices. When the actuator is used as a positionservo mechanism, the output can be applied directly to the compensationnetwork or amplifier. When used as a position servo mechanismincorporating one or more of the actuators, the system will exactlyduplicate manipulations re etitively on command after first being ledthrough the given manipulations and the signal memorized on attendantequipment.

The present invention is adapted to be operated independently of thepressure of fluid acting in the cylinder and is characterized by itsunique arrangement which provides a simplified, low cost structure,having certain advantages contributing to efficiency, reliability andlong life, as well as ease of maintenance.

As previously mentioned, the actuator of the present invention may beutilized in many different applications. One example of an applicationis in conjunction with an industrial type of furnace wherein it isdesirable to move the charge into the furnace a predetermined distance.In such a case, it is not easy to determine the position of the chargein the furnace due to the extreme heat and excessive temperature in thefurnace. With the proposed application, the piston rod is connected tothe movable charging mechanism of the furnace. The relative motion ofthe piston and the cylinder will in turn produce a change in mechanicalenergy of the actuating or follower arm, which change will move the coreof the transducer in a direction to produce a corresponding electricalenergy change in the transducer; A meter is connected to the transducerand calibrated to read in feet or inches so that a change in theelectrical energy in the transducer deflects the needle of the meter apredetermined distance. The meter would indicate the exact position ofthe charge in the furnace.

In addition, this invention is particularly characterized by itsinherent versatility and high performance which makes it suitable forautomation where the output of the device is fed to recorders, dataprocessing and analyst equipment, as well as automatic process systemsand permanently electrically recorded on tape. The tape in turn isutilized subsequently to obtain the exact sequence of mechanical motionfrom the actuating device as is electrically recorded on the tape.

It is an object of the present invention to provide a cylinder andpiston device or the like which emits an electrical signal that isproportional to an increment of stroke.

Another object of the present invention is to provide an actuatingdevice which includes an electro-fluid actuator having a transducerassembly integrally mounted within the cylinder of the actuator, thusproviding flexibility of mounting, minimal design clearance, freedom ofmotion, and compounded angular movements.

Another object of the present invention is to provide an electro-fluidactuator wherein the transducer assembly is mounted on the same axis andintegral with the piston of the cylinder.

A further object of the present invention is to provide an actuatorcomprising a tubular housing member, a wall member in said housingmember, a linear movement camming action stylus in said housing memberand fixedly mounted with respect to one of said members, andelectro-mechanical transducer means carried by the other of said membersand including movable follower means in contact with said stylus, saidtransducer means being effective to convert the relative displacementbetween said members as indicated by the movement of said follower meansinto an equivalent electrical energy change.

A still further object of the present invention is to provide anactuator of the aforementioned type wherein the housing member and thewall member are in the form of a cylinder and piston respectively.

Another object of the present invention is to provide an actuator of theaforementioned type wherein the stylus is fixed to the housing memberand the transducer means is carried by the wall member.

Still another object of the present invention is to provide an actuatorof the aforementioned type wherein the stylus and the housing member areelongated and the stylus has substantially the same longitudinal axis asthe housing member. a

A further object of the present invention is to provide an actuator ofthe aforementioned type wherein the stylus is elongated and theelectro-mechanical transducer means has substantially the same axis asthe stylus.

A still further object of the present invention is to provide anactuator of the aforementioned type wherein means are provided foraligning the axis of the electromechanical transducer means with thelongitudinal axis of the stylus.

Another object of the present invention is to provide an actuator of theaforementioned type wherein the side of the stylus in contact with thefollower means is tapered and the side directly opposite the taperedside is substantially straight.

Still another object of the present invention is to provide an actuatorof the aforementioned type wherein the length of the taper on the stylusis substantially equal to the maximum linear displacement between thewall member and the housing member.

A further object of the present invention is to provide an actuator ofthe aforementioned type wherein means Patented Mar. 23, 1965 areprovided for connecting opposite sides of the wall member to a source oractuatin fluid.

A still further object of the present invention is to provide anactuator, of the aforementioned type wherein a rotatable mounting ringis provided between the wall member and the transducer means forpermitting the wall member to rotate with respect to the transducermeans and vice versa.

Another object of the present invention is to provide a transducerassembly of novel construction and design, the parts of which arearranged to provide a substantially small package.

Still another object of the present invention is to provide a simplifiedlow cost structure of the aforementioned types having certain advantagescontributing to efficiency, reliability, long life as well as to ease ofmaintenance.

Other objects and features of the invention will become apparent as thedescription proceeds, especially when taken in conjunction with theaccompanying drawing(s), wherein: 7

FIGURE 1 is an elevational View, partly in section and withparts brokenaway.

FIGURE 2 is an elevational view of the transducer assembly. I

FIGURE 3 is a vertical sectional view of the transducer assemblyillustrated in FIGURE 2.

FIGURE 4 is an end view looking in the direction of arrows 4-4 of FIGURE2.

FIGURE 5 isavertical sectional view of another em bodiment of thepresent invention.

FIGURE 6 is. a schematic circuit diagram which utilizes a cylinder oractuator incorporating features of the present invention.

FIGURE 1 shows an electro-fluid actuator which consists of a cylinder 10having a piston 12 and a tubular rod 14 movable therein. The cylinder 10is honed to accurate size a 10-15 micro finish to provide long life. andto minimize friction. The piston 12 is of one piece con struction andhas an O-ring seal 11 provided on the inside diameter against the rod14. The piston 12 may be made from a high grade cast iron alloy. Thetubular piston rod 14 is plated with hard chrome and is case hardenedfor protection. A pair of end caps 16, and 18 are provided at oppositeends of the cylinder 10 for closing the interior thereof. The end caps16and 18 are appropriately connected to the cylinder 10 by means of aplurality of threaded fasteners 19 which are received in alignedthreaded openings provided in the end caps and cylinder.

End cap 18 has an annular stepped opening 20 pro vided therein forreceiving a bushing 22 through which the rod 14 extends. The end caps 16and 18 are provided with ports 26 and 28 respectively for supplying anactuating fluid to opposite ends of the cylinder 10. As an example,hydraulic fluid, compressed air or the like, may be utilized. In thepresent application reference will be made to the use of hydraulic fluidfor effecting movement of the piston and rod. assembly. The ports 26 and28 are located in a closed hydraulic circuit 23 which includes ahydraulic servo valve as best illustrated in FIGURE 6.

The end cap 16 is provided with a central opening 30 in which one end 32of an elongated linear movement camming action stylus 34 is mounted. Thestylus 34 is connected to a reinforcing plate 36 by means of a threadedfastener 38, as best illustrated in FIGURE 1. The other end of thestylus 34 is free and extends into the interior of the hollow piston rod14. The stylus 34 is spaced from the interior wall of the rod 14. Thestylus 34 has a longitudinal axis which is in substantial alignment withthe longitudinal axis of the cylinder 10* and the piston and rodassembly. The stylus 34 is precision machined and ground to provideminute accuracy of readings as will subsequently appear.

The stylus 34, as best illustrated in FIGURES 1 and 2,

has an effective length equal to the length of the stroke of the pistonand rod assembly. The transverse crosssectional area of the stylus 34'throughout its effective length constantly decreases from end cap 16 toend cap 18. As illustrated, the stylus 34 is provided with eight sides,the essential feature being that one of the sides of the stylus 34 istapered throughout the effective length of the stylus 34 to provide theconstantlydecreasing crosssectional area as mentioned previously. Thevarious sides of the stylus 34 are identified by the numerals 40, 42,44, 46, 48, 5t 52, and 54. The upperside 40 is provided with a gradualtaper or slope which starts near the end cap 16 and terminates at thefree end of the stylus 34. The inclined sides 42 and 50 aresubstantially parallel as are inclined sides 46 and 54. This isindicated in FIGURE 4. In addition, the vertical sides 44 and 52 arealso parallel to each other and to the longitudinal axis of the stylus34. The remaining bottom or lower side 48 is substantially straightthroughout the effective length of the stylus 34 and is parallel to thedirection of movement of the piston and rod assembly.

In order to electrically reproduce the relative motion of the piston androd assembly and the cylinder 16, a transducer assembly is mounted onthe same axis and integral or movable with the piston 12. By suitablemeans which 'will be subsequently explained the constant varyingcross-sectional area of the stylus 34 or the effective depth of thestylus 34 is transmitted to the transducer 61 which forms a part of thetransducer assembly 60 so that a proportionate output signal isgenerated for each increment of stroke of the piston 12 and rod 14.

The transducer assembly 60 also includes a tubular body 62 whichsurrounds the stylus 34 when in an assembled position. The transducerbody 62 is provided at one end thereof with a radially extending flange64 in which the transducer 61 is mounted. A housing plate 66 is boltedto the flange 64 by means of a plurality of threaded fasteners 68.

A rotatable mounting ring 70 rotates about a needle bearing 72 which isfixed to a piston rod retainer 74. The needle bearing 72, to which thetransducer assembly 60 is connected, allows complete unlimited rotationof the piston 12 and piston rod 14 relative to the transducer assembly60. The piston rod retainer 74 which is also tubular carries the needlebearing 72 on one end and is threadedly connected to the piston rod 14on the other end, as best illustrated in FIGURE 1. The piston rodretainer 74 provides means for holding the piston 12 against theshoulder 76 provided on the piston rod 14. The body 62 of the transducerassembly 60 is connected to the rotatable mounting ring 70 by a pair ofshoulder screws 78, one of which is illustrated in FIGURE 3. A pair ofclosely wound springs 82 and 84 are associated with each of the screws78 and are arranged concentric with the screws 78 so as to act againstopposite sides of the housing plate 66. The shoulder screws 78 andassociated springs provide a transducer assembly centering device whichnegates misalignment of the piston and rod assembly from beingtransferred to the centered transducer 61. v

The body 62 of the transducer assembly 60 is provided with an oilimpregnated bushing through which the reactive core 92 extends. Thereactive core 92 is made from a high grade steel and when in operationdoes not contact thet'ransducer 61. The bushing 90 is effective tocenter the reactive core 92 through continuous cycling of the piston 12.The transducer 61, which is of the fiat coil type, is completelyadjustable for balancing out procedures. Transducer 61 may, as anexample, take the form of a flat coil sensor Model Number D-152-H3manufactured by the Bently Nevada Corporation, lo cated at Airport Road,Minden, Nevada. Complete environmental protection is provided bypressure potting and pressure compensation. The reactive core 92 andtransducer 61 are arranged on the same axis which is substantiallyparallel to the longitudinal axis of the stylus 34. When the core 92 ismoved in a manner to be subsequently explained, a proportionalelectrical energy change is effected in the transducer 61 because of therelative gap 93 between the core 92 and the transducer 61.

The body 62 is provided with two pairs of rotatable bearings 96 and 98.Each pair of guide bearings has the axes of the bearings lying in aplane which is substantially perpendicular to the longitudinal axis ofthe stylus 34. The rotatable guide bearing 96 and 98, as bestillustrated in FIGURES 3 and 4, are adapted to bear against the straightsides 44 and 52 of the stylus 34. The guide bearings 96 and 98 help tocenter the transducer assembly 60 on the stylus 34 for maximum accuracy.The bearings 96 and 98 are rotatably carried by threaded bolts 99 or thelike.

The body 62 is provided with a pair of actuating arms 100 and 102 whichare pivoted to the body 62 by means of bolts 164 on opposite sides ofthe elongated stylus 34. The arms 1% and 102 have offset portions 106which are adapted to carry a shaft 108. Mounted on the shaft 108 is apair of roller bearings 110 and 112 which are adapted to engage the end114 of the core 92. A spring 116 or other resilient means is providedbetween the body 62 and the core 92 for biasing the core 92 against theroller bearings 110 and 112.

A third roller bearing 118 is provided on the shaft 168 intermediate thepair of roller bearings 118 and 112 and is designed to ride along thetapered side 40 of the stylus 34. The spring 116 is effective toindirectly bias the third roller bearing 118 against the tapered side 40of the stylus 34. The force which is induced indirectly by the spring116 biasing the third roller 118 against the tapered side 46 of thestylus 34, is balanced by an additional pair of bearings 120 and 122that contact the bottom straight side 48 of the stylus 34. The bearings120 and 122 are rotatably carried by threaded bolts 124 and 126respectively which are mounted on the body 62 and also held, along withroller 118, to center the transducer assembly 60 on the stylus 34 formaximum accuracy. The core 92 is undercut on its face as indicated at130 so as not to engage the bearing 118.

The variable voltage signal or electrical energy change which isindicated by the transducer 61 is carried from the transducer 61 to apoint outside of the cylinder 19 by a co-axial cable or output lead 138.The co-axial cable 138 is housed or contained within the interior of acoiled nylon tube or shroud 132. The inner end of the tube 132 is fixedto the transducer body 62 by a clamp 134. The coaxial cable 136 emergesfrom the shroud 132 adjacent the end cap 16 and leaves the cylinder bymeans of a pressure-type connector 136 which is fixed to the end cap 16.The cable 131) is potted in a cavity 138 formed in the end cap 16, alongwith electronic circuitry. From the cavity 138 the cable 138 is directedthrough the electrical connector 148, which is a standard conduit typeconnection, to the various attendant electrical instrumentation that maybe required such for an example, the volt meter 180 illustrated inFIGURE 6. The coiled nylon tube 132 acts as a protective shroud againstwear and damage to the cable 130 as it extends and retracts within thecylinder 10 due to the movement of the piston and rod assembly.

A plurality of piston rings 142 are provided around the outer peripheryof the piston 12 and are of the standard automotive type. Cylinder seals144 are provided between the end caps 16 and 18 and the cylinder 10 soas to prevent fluid leakage from the cylinder 10. The seals 144 areleakproof and generally not affected by pressure surges because of thebutt construction. A piston rod seal 146 is provided on the inner end ofthe bushing 22 and is provided with a lip for sealing at low pressures.In addition, a rod wiper seal 148 is provided on the outer end of thebushing 22 which prevents foreign particles or contaminants fromentering the cylinder 10. The seal 148 is effective to wipe the rod 14clean on its outstroke.

The bushing 22 provides accurate centering and side support for thepiston rod 14. The bushing 22 is made of bronze and forms a cartridgewhich is designed for easy removal.

In operation, hydraulic fluid is directed into the interior of thecylinder 10 through the port 26 so as to move the piston 12 and the rod14 which has the work connected thereto to the right. The piston 12 isstroked in opposite directions by a conventional servo valve 25 shown inFIGURE 6. As a result, the transducer assembly 60 is also moved to theright and thereby permits the bearing 118 to ride along the tapered side40 of the stylus 34. The clamping action by hearing 118 and bearings and122 on the stylus 34 necessitates that the transducer assembly 60follows the longitudinal axis of the stylus 34.

Due to the provision of the relative rotary movement between thetransducer assembly 60 and the rotatable mounting ring 70 which ispermitted by the gimbal action between the stud 78, springs 82 and 84and plate 66, the transducer assembly 60 follows the axis of the stylus34 while the housing plate 66 follows the axis of the piston 12. This istrue even though the working axis of the stylus 34 and the Working axisof the cylinder 10 may not always be the same axis due to manufacturing,assembly, unbalanced loading, or other uncontrollable factors.

As a result of the stroking of the piston 12 in opposite directions, thecore 92 will travel back and forth through the bushing 98 as thetransducer assembly 60 and piston 12 travels back and forth in thecylinder 10. The movement of the core 92 is due to the fact that thebearing 118 rides up or down along the tapered side 40 of the stylus 34.The movement of the core 92, which is on the same axis as the transducer61, is effective to vary the gap 93 between the core 92 and transducer61. As the core 92 is moved closer or further away from the transducer61, a proportional electrical energy change, such as a change involtage, is effected. The electrical output signal which is emitted bythe transducer 61 is proportional to an increment of stroke of thepiston 12. The electrical output signal is properly amplified anddelineated through and out of the cylinder 10 by means of the cable orlead 130. The signal thus generated is available to perform any task orreadout that may be required.

FIGURE 5 shows another embodiment of the present invention wherein alinear variable differential transducer (L.V.D.T.) 156 is carried by thebody 158 of the transducer assembly 160 in place of the fiat coiltransducer 61 illustrated in FIGURE 1. Transducer 156, as an example,may take the form of the L.V.D.T. Model No. 350ESL manufactured by theSchaevitz Engineering,.Box 505, Camden, New Jersey. The main core 162 ismovable in an oil impregnated bushing 164 as in the other embodiment andcarries a shaft 166 which in turn carries the transducer core 168. Themovement of the main core 162 is the same as in the other embodiment.The relative motion of the transducer core 168 within the linearvariable differential transducer 156, which is energized, induces avariable voltage output or electrical energy change which isproportional to the relative position of the transducer core 168. Themovement of the main core 162 is dependent on the position of the rollerbearing 170 on the tapered side 40 of the stylus 34 as in the otherembodiment.

The present invention is designed to emit an electrical signal thatvaries proportionally to the effective length of the tapered side of thestylus. The transducer assembly centering device is effective tocompensate for misalignment, as an example up to between the axis of thetransducer assembly 60 and the axis of the stylus 34. The rotation ofthe piston 12 and rod 14 with respect to the cylinder 10 will not rotatethe transducer assembly 60 and such rotation does not effect the outputgun utilized in an automation system.

7 from the transducer 61. The pressure of the spring 116 keeps theroller 118 on the tapered side 40 of the stylus 34. It should beunderstood that the slope of the stylus 34 can be changed to suit anyparticular design or problem.

The present invention is characterized by its inherent versatility whichmakes it suitable for automation. As an example, the circuit illustratedin FIGURE 6 may be constructed and arranged whereby the rod 14 of thehydraulic :cylinder or actuator 10 is connected to a paint Consider themanner and varied operations required to paint the hood of anautomobile. The paint gun, not shown, is placed under the control of thepiston and rod assembly. Movement of the piston and rod assembly movesthe paint gun a corresponding distance. The movement of the piston androd assembly is recorded by feeding the output signal from the co-axialcable 130 to a tape recorder 171 which makes a permanent record on tapeof the various movement required to paint the hood. When the taperecorder 171 is recording the piston and rod assembly is manually movedin the cylinder 10 without the use of any hydraulics from the closedhydraulic circuit 23. The linear displacement or stroke of the piston 12and rod 14 is transmittedto the transducer assembly 60 as mentionedpreviously whereby a proportional output signal is generated for eachincrement of stroke of the piston 12 and rod 14 which in turn isrecorded on the tape. The final result is that a tape is produced whichaccurately records the plurality of movements required to paint the hoodand which may subsequently be utilized to automatically paint otherautomobile hoods.

When it is desirable to utilize the recorded sensing tape from the taperecorder 171 to paint other automobile hoods, the tape, which provides acommand signal on playback, is fed into the function generator 172. Thecommand signal from the generator 172 is directed across the amplifierdevice 174 which includes a summing device 176 and an amplifier 178. Thecommand signal on the output side of the amplifier 178 is directed tothe hydraulic servo-valve 25 which is in turn incorporated with thehydraulic cylinder 10 in the closed hydraulic circuit 23. The commandsignal controls the flow of hydraulic fluid from one cylinder port 26 tothe other port 28. The electrical energy input is transformed into themechanical energy output of the piston and rod assembly which directsthe painting action. When the cylinder 10 is under the direction of thetape, the electromechanical transducer assembly 60 serves the importantfunction of reading and comparing the position of the piston 12 and rod14 with the master tape. The DC voltage signal or output generated bythe transducer assembly 60 is fed through the co-axial cable 130 to thesumming device 176 of the amplifier device 174. Any difference or errorbetween the command signal and the output signal of the transducerassembly 60 in turn produce a correcting signal for the servo-valve 25which in turn directs fluid to the particular port so as to move thepiston and rod assembly to the exact place it should be in the cylinder10 as determined by the command signal on the tape.

A voltage meter 180 is connected to the co-axial cable 130 whereby thevoltage from the transducer assembly 60 can be read direct. This voltageis proportionate to the increment of stroke of the piston and rodassembly.

The drawings and the foregoing specification constitute a description ofthe improved electrohydraulic actuator in such full, clear, concise andexact terms as to enable any person skilled in the art to practice theinvention, the scope of which is indicated by the appended claims.

What I claim as my invention is:

1. An actuator comprising a tubular housing ber, a wall member in saidhousing member, a movement cumming action stylus in said housingmemlinear memher and fixedlymounted with respect to one of said members,and electro-mechanical transducer means carried by the other of saidmembers and including movable follower means in contact with saidstylus, said transducer means being effective to convert the relativedisplace ment between said members as indicated by the movement of saidfollower means into an equivalent electrical energy change.

2. The actuator defined in claim 1 wherein said housing member and saidwall members are in the form of a cylinder and piston respectively.

3. The actuator defined in claim 1 wherein said stylus is fixed to saidhousing member and said transducer means is carried by said wall member.

4. The actuator defined in claim 3 wherein said stylus and said housingmember are elongated and said stylus has substantially the samelongitudinal axis as said housing member.

5. The actuator defined in claim 3 wherein said stylus is elongated andsaid electro-mechanical transducer means has substantially the same axisas said stylus.

6. The actuator defined in claim 3 wherein means are provided foraligning the axis of said electro-mechanical transducer means with thelongitudinal axis of said stylus.

7. The actuator defined in claim 1 wherein the side of said stylus incontact with said movable follower means is tapered.

8. The actuator defined in claim 7 wherein the length of the taper onsaid stylus is substantially equal to the maximum linear displacementbetween said wall member and said housing member.

9. The actuator defined in claim 1 wherein means are provided forconnecting opposite sides of said wall member to a source of actuatingfluid.

10. The actuator defined in claim 3 wherein means are provided betweensaid wall member and said transducer means for permitting relativerotation between said wall member and said transducer means.

11. An actuator comprising a tubular housing, a movable wall in saidhousing, a stylus fixedly mounted in said housing, one side of saidstylus being tapered, and an electro-mechanical transducer assemblyconnected to said wall for movement therewith, said transducer assemblyincluding a transducer and follower means, said follower means being incontact with the tapered side of said stylus for transmitting to saidtransducer a mechanical input signal which is dependent on the positionof said follower means on the tapered side of said stylus as determinedby the movement of said wall, said transducer being effective togenerate an electrical output signal which is proportionate to theaforesaid mechanical input signal.

12. An actuator comprising a tubular housing, a movable wall in saidhousing, an elongated stylus fixedly mounted in said housing, one sideof said stylus being tapered, an electro-mechanical transducer assemblyhaving a longitudinal axis and connected to said wall for movementtherewith, said transducer assembly including a transducer and followermeans, said follower means being in contact with the tapered side ofsaid stylus for transmitting to said transducer a mechanical inputsignal which is dependent on the position of said follower means on thetapered side of said stylus as determined by the movement of said wall,said transducer being eifective to generate an electrical output signalwhich is proportionate to the aforesaid mechanical input signal, andmeans for maintaining the longitudinal axis of said transducer assemblyin substantial alignment with the axis of said stylus.

13. An actuator comprising a tubular housing having a longitudinal axis,a movable Wall spanning the interior of said housing and havingsubstantially the same axis as said housing, an elongated stylus fixedlymounted in said housing and having substantially the same longitudinalaxis as said housing and wall, one side of said stylus being tapered, anelectro-mechanical transducer as sembly having a longitudinal axisconnected to said wall for movement therewith, said transducer assemblyincluding a transducer and follower means, said follower means being incontact with the tapered side of said stylus for transmitting to saidtransducer a mechanical input signal which is dependent on the positionof said follower means on the tapered side of said stylus as determinedby the movement of said wall, said transducer being effective togenerate an electrical output signal which is proportionate to theaforesaid mechanical input signal, and means for maintaining the axis ofsaid transducer assembly in substantial alignment with the axis of saidstylus.

14. The actuator defined in claim 13 wherein said movable wall is in theform of a piston and rod assembly.

15. The actuator defined in claim 14 wherein one end of said stylus isfixed to an end wall of said cylinder and the other end is free.

16. The actuator defined in claim 15 wherein said piston and rodassembly is tubular and said other end of the stylus is received withinthe interior of said piston and rod assembly.

17. A transducer assembly comprising a tubular body having alongitudinally extending axis, a transducer carried by said body, amovable core having one end opposite said transducer, said core and saidtransducer having an axis which is substantially parallel to thelongitudinal axis of said body, an actuating arm pivoted to said bodyabout an axis extending transversely to the longitudinal axis of saidbody, and a roller bearing carried by said arm in contact with the otherend of said core, said roller bearing being ellective to move said corewith respect to said transducer in response to the movement of said armto produce a change in the electrical energy output of the transducer.

18. The transducer assembly defined in claim 17 wherein resilient meansare provided between said body and said core for biasing said coreagainst said bearing.

19. The transducer assembly defined in claim 17 where in a pair ofactuating arms are provided, said arms being connected by a shaft, and apair of roller bearings carried by said shaft and in contact with saidother end of said core.

20. The transducer assembly defined in claim 19 Wherein a third rollerbearing is carried by said shaft intermediate the other of said rollerbearings, said third roller being spaced from said other end of saidcore.

References Cited by the Examiner UNITED STATES PATENTS 2,362,151 11/44Ostenberg 290-1 2,778,986 1/57 Eklund 336- 30 2,788,665 4/57 Wiancko336- 2,977,765 4/6 1 Fillmore 91-363 3,083,321 3/63 Howe 318l9 3,104,3499/ 63 Stevens 318-22 3,105,153 9/63 James, Jr. 290-1 MILTON O.HIRSHFIELD, Primary Examiner.

1. AN ACTUATOR COMPRISING A TUBULAR HOUSING MEMBER, A WALL MEMBER INSAID HOUSING MEMBER, A LINEAR MOVEMENT CAMMING ACTION STYLUS IN SAIDHOUSING MEMBER AND FIXEDLY MOUNTED WITH RESPECT TO ONE OF SAID MEMBERS,AND ELECTRO-MECHANICAL TRANSDUCER MEANS CARRIED BY THE OTHER OF SAIDMEMBERS AND INCLUDING MOVABLE FOLLOWER MEANS IN CONTACT WITH SAIDSTYLUS, SAID TRANSDUCER MEANS BEING EFFECTIVE TO CONVERT THE RELATIVEDISPLACEMENT BETWEEN SAID MEMBERS AS INDICATED BY THE MOVEMENT OF SAIDFOLLOWER MEANS INTO AN EQUIVALENT ELECTRICAL ENERGY CHANGE.
 9. THEACTUATOR DEFINED IN CLAIM 1 WHEREIN MEANS ARE PROVIDED FOR CONNECTINGOPPOSITE SIDES OF SAID WALL MEMBER TO A SOURCE OF ACTUATING FLUID.